Roman
Calendar - Why 28 days in February?

We
owe the modern calendar's differing number of days each month to
the Romans. The early Roman calendar consisted of 12 months beginning
in March like this (later January became the start of the year):

Month

Length

Martius

31

Aprilis

29

Maius

31

Iunius

29

Quintilis

31

Sextilis

29

September

29

October

31

November

29

December

29

Ianuarius

29

Februarius

28

Februarius
(leap years)

23

Intercalaris
(leap years)

27/28

The
early Romans attempted to syncronize the months with the first crescent
moon following a new moon resulting in some months of 29 days and
some of more.

Every
other year, February was shortened and a leap month (Intercalaris)
was added in an attempt to realign lunar cycles with the solar calendar.
The lengths of the years in a four year cycle of this lunisolar
calendar were 355, 377, 355, and 378 days. This added up to 4 days
too many to stay in sync with the solar year.

Julian
Calendar

Eventually
Julius Caesar asked an astronomer, Sosigenes of Alexandria, Egypt,
to devise a better calendar. What resulted is called the Julian
Calendar. He abandoned aligning the months with lunar cycles, and
adopted months of 30 or 31 days length, keeping February at 28 days.
He introduced an extra day in February in leap years. Sound familiar?